1. Field of the Invention
This invention relates generally to write drivers, and more particularly, to a technique for enhancing the performance of inductive recording head write drivers.
2. Description of the Prior Art
H-switch drivers are used in magnetic disk drives to supply write current to the inductive recording head to write data to recording disks. An H-switch generally includes four transistor switches, each forming one leg of the H. A write head coil is then connected to terminals across the center span of the H. Current is passed through the coil in a first direction by operating two of the transistor switches in opposite legs of the H-switch. Similarly, current is passed through the coil in the opposite direction by operating the remaining two transistor switches.
Write drivers for inductive write heads require a stout pull-up at the upper H-switch to achieve fast switching. Generally, a low-valued resistor is used in the pre-driver to accomplish the desired pull-up, which results in considerable power dissipation. U.S. Pat. No. 6,184,727, entitled Write Driver Circuit Having Enhanced Switching Control Circuitry, issued Feb. 6, 2001 to Price, Jr., describes use of control signals to achieve fast switching; but this technique does not provide the optimal control signal timing necessary to achieve fast switching.
In view of the foregoing, it would be desirable and advantageous to provide a technique for presenting an optimally timed control signal to an upper H-switch driver in a fashion capable of achieving a very fast transition of the current in the inductive recording head. It would also be desirable and advantageous if the technique could provide a current boost during the transition while resulting in minimized power consumption at other times.
The present invention is directed to a system and method for enhancing the performance of inductive recording head write drivers.
In one aspect of the invention, a system and method provides an optimally timed control signal to an upper H-switch driver to achieve a very fast transition of the current in the inductive recording head.
In another aspect of the invention, a system and method provides an inductive recording head current boost during the transition of the current in the inductive recording head, while resulting in minimized power consumption at other times.
One embodiment of the invention is directed to a write current driver circuit comprising an H-switch driver having first and second upper switches and further having first and second lower switches, wherein the H-switch driver is operational to direct write current in opposite directions through a write head connected between a first node connecting the first upper switch to the first lower switch and a second node connecting the second upper switch to the second lower switch in response to first and second input signals; a first current pulse generator; and a first inverter circuit operational to generate a switching signal to the first lower switch in response to the first input signal, wherein a supply current associated with the first inverter circuit is processed by the first current pulse generator to provide a high current pulse to the first upper switch to accelerate a write current transition associated with the first upper switch.
Another embodiment of the invention is directed to a write current driver circuit comprising an H-switch driver having first and second upper switches and further having first and second lower switches, wherein the H-switch driver is operational to direct write current in opposite directions through a write head connected between a first node connecting the first upper switch to the first lower switch and a second node connecting the second upper switch to the second lower switch in response to first and second input signals; means for generating a first current pulse; and means for generating a switching signal to the first lower switch in response to the first input signal, wherein a supply current associated with the means for generating a switching signal to the first lower switch is processed by the means for generating a first current pulse to provide a high current pulse to the first upper switch to accelerate a write current transition associated with the first upper switch.
Still another embodiment of the invention is directed to a method of accelerating write current transitions associated with the upper switches of a magnetic recording head H-switch driver comprising the steps of providing a write current driver having an H-switch, first and second current pulse generators, and first and second inverters; generating a switching signal via the first inverter to a first lower switch associated with the H-switch in response to a first input signal; and processing a supply current associated with the first inverter via the first current pulse generator to provide a high current pulse to a first upper switch associated with the H-switch to accelerate a write current transition associated with the first upper switch.